the trigeminal sense
The trigeminal sense is a second system in the nose, stemming from the trigeminal nerve (one of the twelve cranial nerves), which also detects smells. However, the trigeminal sense only seems to react to common odors, such as foods (i.e. burning taste of chili peppers, horseradish) and cigarette smoke. Technically, though, the trigeminal sense is not actually a "second sense of smell."
